#include <bits/stdc++.h>
using namespace std;

int main()
{
	string S;
	cin >> S;

	int N = S.size();
	int ans = 0;
	int flag = 0;
	for( int i = 0; i < N; i++ ) {
		if( i + 4 <= N && S.substr( i, 4 ) == "pain" ) {
			flag = 1;
			break;
		}
		if( i + 3 <= N && S.substr( i, 3 ) == "pon" ) {
			i += 2;
			ans++;
		}
	}
	if( flag == 0 || ans < 2 ) ans = -1;
	else ans--;

	cout << ans << endl;
}